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Abstract

We explore a method to quantitatively assess the ability of in vivo autofluorescence as a means to quantify the progression of longer periods of renal warm ischemia and reperfusion in a rat model. The method employs in vivo monitoring of tissue autofluorescence arising mainly from NADH as a means to probe the organ’s function and response to reperfusion. Clinically relevant conditions are employed that include exposure of the kidney to ischemia on the order of tens of minutes to hours. The temporal profile during the reperfusion phase of the autofluorescence intensity averaged over an area as large as possible was modeled as the product of two independent exponential functions. Time constants were extracted from fits to the experimental data and their average values were found to increase with injury time.

(A) Normalized autofluorescence spectra of a rat kidney in vivo before ischemia (solid), following 150’ of ischemia (dash-dot), and following 90’ of reperfusion (dotted). (B) (147 kB) Movie of the normalized spectrum during 150’ injury and 90’ reperfusion. (C) The ratio of the spectrum after 150’ of injury to the spectrum at the given time point into injury. (D) (133 kB) Movie of this ratio during 150’ injury and 90’ reperfusion. [Media 1][Media 2]

Tables (2)

Table 2: Statistical analysis results. On the left, average values of extracted time constants with standard deviations (and number of rats in parentheses). On the right, pairwise comparison of injury time points (20, 50, 150 minutes) using Tukey test statistic q5%=3.47. Asterisks indicate significance at the 0.05 level.

Mean±SD of ΔI parameter separated by behavior type for the different injury time groups.

** denotes significance at the 0.005 level. Number of rats per group is indicated in parentheses.

Table 2:

Statistical analysis results. On the left, average values of extracted time constants with standard deviations (and number of rats in parentheses). On the right, pairwise comparison of injury time points (20, 50, 150 minutes) using Tukey test statistic q5%=3.47. Asterisks indicate significance at the 0.05 level.

Injury Time (mins.):

20

50

150

20,50

20,150

50,150

Δτ

1.30

6.96*

5.66*

Total

2.3±1.8 (12)

3.9±3.1 (12)

11.2±6.8 (12)

Behavior 1

3.5±1.3 (5)

3.3±1.4 (6)

11.9±11.7 (4)

Behavior 2

1.4±1.7 (7)

4.6±4.3 (6)

10.8±3.5 (8)

τN

0.03

4.10*

4.07*

Total

2.8±2.7

2.9±2.5

6.2±3.3

Behavior 1

5.2±2.8

3.2±3.3

5.7±0.5

Behavior 2

1.1±0.6

2.5±1.6

6.5±4.1

τE

1.78

9.05*

7.27*

Total

5.7±2.8

9.8±5.3

26.4±12.3

Behavior 1

7.7±2.0

6.0±3.7

21.6±1.9

Behavior 2

4.3±2.5

13.6±3.6

28.7±14.7

Tables (2)

Table 1.

Mean±SD of ΔI parameter separated by behavior type for the different injury time groups.

** denotes significance at the 0.005 level. Number of rats per group is indicated in parentheses.

Table 2:

Statistical analysis results. On the left, average values of extracted time constants with standard deviations (and number of rats in parentheses). On the right, pairwise comparison of injury time points (20, 50, 150 minutes) using Tukey test statistic q5%=3.47. Asterisks indicate significance at the 0.05 level.